1. Field of the Invention
The present invention relates to a method for preparing a red ginseng saponin extract in which saponin components and non-saponin components are extracted from red ginseng and the non-saponin components are selectively removed from the red ginseng extract to prepare a red ginseng extract containing large amounts of the saponin components, and a red ginseng saponin extract prepared by the method.
2. Description of the Related Art
Ginseng radix refers to the root of Panax ginseng C. A. Meyer, which is a perennial herb belonging to the Araliaceae family. Ginseng radix is classified into fresh ginseng, red ginseng, and white ginseng by their processing methods.
Fresh ginseng is ginseng that is not processed after it has been harvested from the cultivation farm. Fresh ginseng has a high water content of 70 to 80% and is thus difficult to store for a long period of time. White ginseng is prepared by peeling off the bark of fresh ginseng or drying harvested fresh ginseng under natural sunlight or with hot air. White ginseng has an ivory-white or light yellow color. Red ginseng is prepared by washing unpeeled fresh ginseng, followed by a series of steaming and drying processes. Red ginseng is light yellowish-brown or dark red in color.
Ginseng radix has many efficacies, such as enhancement of physical strength and stamina, hematosis, body heat retention, improvement of fatigue resistance, mental stability, and sedation, which are known to be mainly due to the presence of ginseng saponins.
Saponins are classified into three groups according to their chemical structures: protopanaxadiol, protopanaxatriol, and oleanolic acid. It is known that such saponins have great influences on the regulatory systems, such as the central nervous system, the endocrine system, the immune system, and the metabolic system, and as a result, they are very effective in the regulation of body functions, that is, the normalization of physiological functions.
Red ginseng contains glycosides, panacen, polyacetylene compounds, nitrogenous ingredients, flavonoids, vitamin B complex, trace elements, enzymes, antioxidants, organic acids, and amino acids, like fresh ginseng. Particularly, fresh ginseng experiences many chemical modifications, such as saponin modifications, amino acid changes, and browning, during steaming and drying for the preparation of red ginseng. At this time, saponin components, such as ginsenosides Rg2, Rg3, Rh1, and Rh2, which are peculiar to red ginseng and are not found in fresh ginseng, are newly created. Such red ginseng saponins are known to exhibit cancer prevention, cancer cell growth inhibition, hypotensive, brain cell protection, learning ability improvement, antithrombotic, and antioxidant actions, which are responsible for outstanding pharmacological effects of red ginseng.
However, red ginseng is hardened after drying and is thus inconvenient to directly ingest. Red ginseng is usually taken in the form of a water extract. In recent years, red ginseng concentrates have been popularized for their ease of drinking and storage. For these reasons, most red ginseng processed products are currently being distributed in the form of red ginseng concentrates and products containing them.
The content of saponins in a red ginseng extract is indicative of quality of the red ginseng extract and varies depending on various factors for the extraction of red ginseng. Such factors include physical factors, such as extraction solvent, temperature and time, and chemical factors, such as organic acids present in the extract. Even when only one of these factors is changed, the content of saponins in the extract varies greatly.
According to a widely used traditional method for the preparation of a red ginseng extract, red ginseng is generally extracted with water as an extraction solvent at a high temperature of 85 to 90° C. for 24 to 48 hours. However, the long-term treatment with hot water leads to the degradation of saponins as active ingredients of red ginseng, which is affected by organic acids present in the red ginseng during extraction.
In an attempt to solve this degradation problem, extraction of red ginseng with ethanol as an extraction solvent under heating instead of water is proposed. However, the use of ethanol as an extraction solvent leads to low extraction yield compared to the use of water, produces a strong unpleasant smell, such as an earthy smell, and incurs loss of the original flavor of red ginseng.
Many efforts have been made to solve the above problems. For example, Korean Patent No. 1095357 discloses a method for preparing a processed ginseng radix extract including treating ginseng radix with acidic or alkaline electrolyzed water at a temperature of 50 to 80° C., steaming the treated ginseng radix at a temperature of 90 to 120° C. for 0.5 to 15 hours, and extracting the processed ginseng radix with water, a C1-C4 alcohol or a mixed solvent thereof.
According to this method, the treatment of ginseng radix with acidic and/or alkaline electrolyzed water can efficiently increase the contents of ginsenosides Rg2, Rg3, and Rg5 and can prevent side effects caused by the remaining solvent. However, the bitter taste of particles present in the processed ginseng radix or the processed ginseng radix extract causes a feeling of repulsion upon taking. The extraction with water increases the dissolution of starch particles. The starch particles tend to discolor with time, which causes deterioration of marketability of the ginseng radix extract.
Another method for preparing a red ginseng extract is disclosed in Korean Patent No. 1151722. According to this method, alkaline water at a pH of 8.5 to 10.5 is added to red ginseng, the red ginseng is extracted at 65 to 90° C. for 1 to 12 hours, the extraction is repeated 1 to 10 times, the extract is filtered to remove insoluble matter, and the filtrate is sterilized, filtered, and concentrated. Through the series of processing steps, the red ginseng extract has increased contents of ginsenosides Rg1 and Rb1.
The alkaline water has a higher pH than general water and acts as stabilized water that inhibits ingredients of the extract from being changed. The alkaline water suppresses the conversion of ginsenosides present in ginseng radix or red ginseng to ginsenosides Rh1, Rg2, and Rg3, achieving increased contents of ginsenosides Rg1 and Rb1 after extraction.
If the extraction temperature, the extraction time, and the number of times of extraction are less than the lower limits defined above, the extraction yield is lowered. Meanwhile, if the extraction temperature, the extraction time, and the number of times of extraction exceed the upper limits defined above, ginsenosides and other useful physiologically active ingredients are degraded. Although the extraction temperature, the extraction time, and the number of times of extraction are within the respective ranges defined above, the degradation of ingredients proceeds with increasing extraction yield, impeding the extraction of useful ginsenosides in high yield.
Since the particles present in the extract are very fine and exist in a suspended form, they are not sufficiently removed by general separation methods, such as filtration or centrifugation, leaving residue in the final red ginseng extract. The residue is bitter in taste, which deteriorates the marketability of the red ginseng extract, discolors the red ginseng extract during long-term storage, and forms a precipitate, which is a factor deteriorating the storage stability of the red ginseng extract.
Saponin components and non-saponin components coexist in the extract. Non-saponin components are usually present in a larger amount in the red ginseng than saponin components but are not completely separated from saponin components by the method. Therefore, the content of saponins as active ingredients in the final red ginseng extract is lowered and the saponins are slowly degraded by organic acids present in the red ginseng.
Further, Korean Patent Publication No. 2010-0005828 discloses a method for preparing a red ginseng concentrate by which the degradation of saponins during extraction of red ginseng can be minimized. According to this method, red ginseng is extracted with 30% ethanol, edible soda as a neutralizing agent is added to the extract to neutralize organic acids, and the extraction is repeated 4 times at a temperature of 80° C. for 10 hours. The ethanol extraction reduces the amount of starch extracted compared to water extraction and can inhibit the degradation of saponins. The neutralization prevents the degradation of saponins caused by organic acids.
However, when the red ginseng concentrate is filtered, large solid particles present in the concentrate are removed but fine solid particles are not easily removed. As a result, the taste of the red ginseng concentrate is still bitter, the storage stability of the red ginseng concentrate is deteriorated, and the content of saponin components in the red ginseng concentrate is not increased to a high level due to the coexistence with non-saponin components.
Attempts have steadily been made to extract large amounts of saponin components from ginseng radix or red ginseng in high yield. However, none of the attempts have been succeeded in increasing the contents of saponins to satisfactorily high levels. Further, impurities present in red ginseng extracts are difficult to sufficiently remove, and as a result, the red ginseng extracts tend to discolor or precipitate during long-term storage. These problems remain unsolved.
Most commercially available red ginseng extract products are prepared by concentrating red ginseng extracts to high levels or formulating red ginseng extracts into powders or tablets for longer shelf life. However, beverages or liquid preparations containing red ginseng extracts are not yet commercialized.